1. Field of the Invention
The present invention relates to a communication node accommodating terminals of various kinds of media connected via various kinds of lines such as a high-speed digital leased line, an ultra-high-speed digital leased line, an ATM megalink service, and the like, and more particularly to an intranode alternate route generation method and apparatus for generating an alternate route as needed within the communication node when a failure or congestion occurs in line control equipment in a line accommodating section of the node.
2. Description of the Prior Art
FIG. 1 is a diagram showing one example of a communication node to which the present invention is applied.
In FIG. 1, the node 1 is a node generally called an ATM-WAN (Asynchronous Transfer Mode Wide Area Network) node which performs ATM transmission to and from other nodes by cell-multiplexing information from terminals of various media using lines such as a high-speed digital leased line, an ultra-high-speed digital leased line, an ATM megalink service, and the like.
As shown in FIG. 1, the node 1 accommodates, in addition to a conventional PBX and data terminals 2, various kinds of communication media such as a frame relay unit 4, ATM terminals (ATM TEs) 8, a time division unit (TDM) 5, a multiplexing unit (MIX) 6, and a wide area network (WAN) 7. The node 1 converts a signal from each of the media into an ATM signal which is then cell-multiplexed for ATM transmission over a high-speed line 9 to another similar node. Thus, a wide area network using ATM (ATM-WAN) is formed by interconnecting a plurality of such nodes 1.
FIG. 2 is a diagram showing an example of the basic configuration of a line accommodating section in the node 1 of FIG. 1.
In FIG. 2, line connection equipment 15 accommodates subscriber lines 17 to which the various kinds of media are connected. The example of the line connection equipment 15 shown here accommodates a conventional PBX and data terminals or the like, and is tasked with terminating voice/data signals transferred between the PBX and the data terminals, etc. and with performing the mapping between the terminated signals and prescribed time slot signals time-division multiplexed in units of slots on a TDM bus 18 within the node.
A time-division switch (TSW) 13 is responsible for the switching and path management of each of the time slot signals flowing along the TDM bus 18. In the path management, one or more time slot signals are assigned onto the TDM bus 18 in accordance with the bandwidth of each subscriber contract line. In this way, a path bandwidth is assigned for each logical path of a subscriber onto the TDM bus 18.
Clad equipment (CLAD) 14 is a TDM-ATM conversion processing unit which performs conversion to and reconversion from ATM cells by performing cell assembly/disassembly between the prescribed time slot signal flowing along the TDM bus 18 and the ATM cell signal on a UTOPIA bus 16 along which ATM cells flow.
An ATM switch (ATM-SW) 12 is an exchange apparatus for switching the ATM cell signal on the UTOPIA bus 16. Control equipment 11 is a central processing unit of the node 1 and performs control of all the units and lines accommodated in the node 1 via the control paths shown by dashed lines in FIG. 2.
FIG. 3 is a diagram showing an example of the configuration of a line accommodating section in a prior art node.
In FIG. 3, the same parts as those shown in FIGS. 1 and 2 are designated by the same reference numerals, and such parts will not be further described here. The line accommodating section of the prior art comprises a line connection equipment 15 and line control equipments 14-1 and 14-2 arranged in a dual configuration. Each line control equipment 14-1 or 14-2 corresponds to the clad equipment 14 of FIG. 2, one being configured as a working unit and the other as a backup unit.
In this configuration, when a failure occurs in the working line control equipment 14-1, rendering it unusable or inoperative, control is switched to the backup line control equipment 14-2 in order to maintain and continue the current communication conditions. In this way, for the selection/generation of an alternate route within the prior art node 1, the backup equipment 14-2 dedicated to alternate routing is provided and, in the event of a failure or the like, the lines accommodated in the failed equipment 14-1 are immediately switched to the backup equipment 14-2 to form the alternate route.
In the prior art, therefore, since redundant equipment dedicated to alternate routing has had to be provided, the number of equipments that can be used in normal operation has been limited, leading to the problem that the equipment utilization in the node as a whole is reduced or limited. The prior art configuration described above has also had the problem that when a failure also occurs in the backup equipment (a double failure), no further alternate routing can be performed.
In view of the above-outlined problems, it is an object of the present invention to provide an intranode alternate route generation method and apparatus wherein, in a node having a line accommodating section comprising a plurality of line connection equipments and line control equipments, when a failure or congestion occurs in one line control equipment, an alternate route is formed by using idle logical channels available in another operating line control equipment.
It is another object of the present invention to provide an intranode alternate route generation method and apparatus wherein, when the failed line control equipment is restored from the failure or congestion, the alternate route provided in another line control equipment is released and switched back to the original route.
It is a further object of the present invention to provide an intranode alternate route generation method and apparatus wherein, when performing the selection or switching back of the alternate route, the route is selected for the most suitable line control equipment at that time using statistical information on failure/congestion, etc. or the route is switched back accordingly.
The intranode alternate route generation method and apparatus are applied to all operating line control equipments, and their alternate routes are dynamically generated/formed and released. Accordingly, in the present invention, there is no need to provide redundant equipment such as backup equipment, and if one line control equipment becomes unusable, the efficiency of equipment operation is unaffected as long as corresponding idle logical channels are available in other equipment.
Furthermore, as long as idle logical channels are available in other equipment, line control operations can be continued without interruption even in the event of a double failure condition. Furthermore, when selecting or restoring the route, the most suitable line control equipment at that instant in time is selected based on the failure/congestion statistical information, ensuring proper equipment operation and maintenance.
According to the present invention, there is provided, in a node having a line accommodating section comprising a plurality of line connection equipments and line control equipments and an exchange section for performing switching of signals supplied from the line accommodating section, an intranode alternate route comprising: detecting means for detecting an unusable condition when any one of the line control equipments becomes unusable; extracting means for extracting idle channels from channels accommodated in another operating line control equipment when the unusable condition is detected; and linking means for dynamically linking the channels accommodated in the unusable line control equipment to the extracted idle channels, in that other operating line control equipment, by way of an alternate route.
Preferably, one or more line control equipments are designated by the linking means as destinations of the linking. When the line control equipment designated by the linking means as the destination of the alternate route becomes unusable, an alternate route is formed to still another operating line control equipment.
The detecting means further detects a usable condition when said unusable line control equipment is restored and becomes usable and, in response to the detection of the usable condition, the linking means switches back the alternate route associated with the channels originally accommodated in the restored line control equipment. When switching back the alternate route, the linking means uses basic route information which records initially accommodated channels for each line control equipment.
The apparatus further includes information collecting means for collecting information concerning the condition of each line control equipment, and based on the information from the information collecting means, the extracting means preferentially extracts idle channels from channels accommodated in a line control equipment having higher reliability. The information collected by the information collecting means contains the number of idle channels, the number of occurrences of a failure, resource information, or load information for each line control equipment. In this case, alarm means outputs alarm information when the total number of idle channels available between each line control equipment drops below a predetermined value.